BranchCache Migration Guide

BranchCache is a feature of Windows Server® 2008 R2 and Windows® 7 client that enables clients in a branch office to securely retrieve files that are cached locally instead of having to retrieve files from a home office server. Since branch offices are typically connected over slow wide area network (WAN) links, this reduces the utilization of the WAN link and increases application responsiveness as seen by clients.

This guide describes how to migrate a server that is using BranchCache capabilities to another machine running Windows Server 2008 R2. Migration involves moving current BranchCache cache data and registry settings from a source server to a destination server.

BranchCache can operate in one of two modes.

In the Hosted Cache mode, a dedicated BranchCache™ server in the branch running Windows Server 2008 R2 hosts the cached files. Clients maintain their own local cache of files that they downloaded from home or branch office servers. However, because of the dedicated BranchCache server in the branch office, WAN utilization is reduced in this mode.

In the Distributed Cache mode, a branch server is not required, as copies of files are directly cached on computers in the branch and made discoverable to other Windows 7 clients as needed. In this scenario, the BranchCache™ server at headquarters receives a client file request, and if the file was previously requested, the remote site will return a set of hash directions to the file’s location on the remote network, usually another user’s computer. Files are then discoverable in this location. If file versions are different, files are given different hashes to prevent out-of-date files from being downloaded within the branch. If the file was never requested or if the user who previously requested the file is off-site, then the request is fulfilled generally across the WAN.

BranchCache only serves files to users who have the appropriate permissions and checks are made to make sure that the latest version of the file is delivered.

This guide describes how to migrate a server that is using BranchCache capabilities to another computer that is running Windows Server 2008 R2.

Migration documentation and tools ease the migration of server role settings and data from an existing server to a destination server that is running Windows Server 2008 R2. By using the tools that are described in this guide, you can simplify the migration process, reduce migration time, increase the accuracy of the migration process, and help to eliminate possible conflicts that might otherwise occur during the migration process. For more information about installing and using the migration tools on both source and destination servers, see the Windows Server Migration Tools Installation, Access, and Removal Guide (http://go.microsoft.com/fwlink/?LinkId=134763).

This document is intended for information technology (IT) administrators, IT professionals, and other knowledge workers who are responsible for the operation and deployment of the File or Web servers or dedicated Hosted Cache servers in a managed environment. Some scripting knowledge may be required to perform some migration steps that are contained in this guide.

Foundation, Standard, Enterprise, and Datacenter editions of Windows Server are supported as either source or destination servers.

Note

Hosted cache functionality is not available on Standard servers.

Migration from a source server to a destination server that is running an operating system in a different system user interface (UI) language than the source server is not supported. The system UI language is the language of the localized installation package that was used to set up the Windows operating system. For example, you cannot use Windows Server migration tools to migrate roles, operating system settings, data, or shares from a computer that is running Windows Server 2008 in the French system UI language to a computer that is running Windows Server 2008 R2 in the German system UI language.

BranchCache is a feature of Windows Server 2008 R2 and Windows 7 client that enables clients in a branch office to securely retrieve files from within the branch office when available instead of having to retrieve files from the server. There are no dependent roles that have to be migrated.

The migration of BranchCache dedicated server and feature takes two to three hours, including testing.

The following illustration shows that the pre-migration process involves the manual collection of data, followed by running procedures on the destination and source servers. The migration process includes source and destination server procedures that use the Export and Import cmdlets to automatically collect, store, and then migrate server role settings. Post-migration procedures include verifying that the destination server successfully replaced the source server and then retiring or repurposing the source server. If the verification procedure indicates that the migration failed, troubleshooting begins. If troubleshooting fails, rollback instructions are provided to return the network to the use of the original source server.

The BranchCache service must be stopped on the source server in order to perform the migration. Therefore, BranchCache-related capabilities will be unavailable on the source server until the migration is completed.

Although this migration has no effect on other servers in the enterprise during and after migration, clients will experience decreased performance while downloading files during the migration process and will not see BranchCache feature benefits until the service on the destination server is re-started after the migration has completed.

When the migration is completed, and if server name and IP address was not migrated from the source server to the destination server, clients then have to be pointed to use the new hosted cache as described in the topic BranchCache Migration: Post-migration Tasks, section "Restart and reconfigure the service".

Migration – For a server configured as a hosted cache, it may take from several minutes to several hours, depending on the size of the cache of data that has to be migrated. By default, a hosted cache is configured to have a cache that is 5% of the hard disk drive size. Administrators are encouraged to increase that default to a larger percent during the initial deployment of BranchCache. For a Web server that has BranchCache enabled, it should take several minutes.